Process for the production of potassium manganate



l lusite), whilst providing simultaneously for Patented Oct. 1 93 1UNITEDfS TA TES -TENT Farce ALFRED FELIXSEBASTVIENBELLONE, or LYON,FRANCE, ASSIGNOR TO socnirrn nus USINES CHIMIQUES RHGNE-POULENC, orPAR-IS, FRANCE PROCESS FOR THE PRODUCTION OF POTASSIUM MANGANATE NoDrawing. Application filed hpril 28, 1928, Serial No. 273,774, and inFrance June 29, 1927.

The invention relates to a process for the productlon of postassluln'manganate. It

has over the known process the advantage that aqueous caustic potash canbe used at relatively low temperatures and without great expenditure ofpower.

' The process consists essentially in blowing oxygen through aqueous,hot caustic potash, which contains in a suspended state the manganesedioxide (manganese peroxide or pyrothe intimate contact between gas andliquid.

The temperature to be employed can vary between fairly large limits; itmust,'however, in all cases be suificlent tomaintaln the'mass 1n aliquidstate. v

In practice it is desirable to use caustic I potash of 7 0% to 85%, and,in these conditi'ons, a temperature between 160 and 220 C. thensufiices, in general, in order to obtain sion' of the manganese dioxide.

" tion is, however, limited neitherto this concentration nor to thetemperatures mentioned. Concentration of 60% and less, for example,likewiseproduce good results, provided that the temperature, admissionof the gas and the duration are chosencorrespondingly, so that ;apartial removal of thewater is ensured.

Concentrations over 85% can be used, but

' therefore, liquid to the end, which permits of using intensive'mixingdevices.

In order that the reaction mass remains liquid to the end, an excess'ofcaustic'potash must naturally be used. The caustic potash which does nottakepart in the reaction can easily be recovered, for example, bylixiviating the reaction mass with small quantitiesot water or ofdiluted caustic potash lye, or

' by simple decantation of the molten mass; in 7 this latter case,ahighly concentrated caustic potash lye is obtained, which can bedirectly.

used again. Themanganate, and the impurities of the manganese dioxide,if any, accumulate almost entirely in the lower layer.

The oxygen may contaln other gases which are-neutral'to the substancestaking part in the reaction; thus ordinary air may beused, which isparticularly cheap, since no increased pressure is needed.

Natural and synthetic manganese dioxide can be used in the process; butother oxides of manganese or compounds which give such oxides, can alsobe used and converted according to this process into manganate;compounds of'manganese oxides with basescan also be used.

A more rapid conversion into 'manganate is obtained by first treatingthe manganese dioxide or other manganese compounds for some time withthe molten caustic potash and then blowing in the oxygen or the gasmixtures mentioned. quickly a complete or nearly complete conver- Theinvenv Example 1 I I 6 kgs. of 75% caustic potash are melted'in 'avessel provided with a stirring apparatus,

heated to 180 (3., 1 kg. ofnatural manganese peroxide ofabout 90% beingadded.

A stream of air free of carbondioxideis then directedinto the moltenmass with a rateof flow. of about 300 litres per hour, the

mass being kept at180 C., with stirring. After 18 hours the dioxide isalmost quantitatively converted into manganate; the excess causticpotash is separated without difliculty, as,for example, by decanting at180 C.

Example 2 1.250 kg. of manganese dioxide and 4 litres of potash lye ofare introduced into the same apparatus as used in Example 1. A stream ofair (1000 litres per hour) is passed through the mass while it isstirred, and heat is applied so, that the water evaporates. A further 2litres of lye are added gradually; a temperature of 210 C. is thusobtained, and

is maintained for the whole duration of the reaction. After 12 hours theconversion is almost quantitative. The mass is then treated with adiluted potash lye and the manganate is separated from the alkali bydecantation. f

In the same apparatus as used in the pre- 1 ceding EXa1nples,5.500kgs.of caustic potash V r of .81% are melted, 1 kg. of pyrolusite' is Iadded and the temperature is brought to'and I with an oxygen gasometerwhereby the ab-- f sorption of the oxygen takes place Ver'y'rapidr V.1y,so that after 8 hours the'conversion is completed; separation iselfected. as above men-. v

1 amp 3' Q maintained at 180 C, Connection is made tioned.

What I claim and desire to secure by Let a' ters Patent is v H e a 1;The process for the Y of melted aqueous caustic potash in which a-;quantity.required. o a H lntestimony whereof ll have signedl' mymanganese compound is suspended; rnaintaining the concentration of thesaid melted aqueous; caustic potash loetween 65%;and ,85%throughout theoperation, and causing 'the reaction to proceed'at a temperature of 150to 220 (3.. V

-,2, The process according to claim 1, in Whichthe manganese compound isa mangainese 0Xide.. w

3; The process for the production of potassium manganate which consistsin blow- :ing agascontaining oxygen into an excess of melted aqueouscautic potash in which a nanganese cmnp ound is suspended," andmaintaining the concentration of the said whichv the excess of melted,aqueous; cautic potash "is more than twicegthe jthgQre ical I V 7 nameto this specification.

I production" of potass um manganate WlllCll consists 1nbl0W- i ing agELSCOIltELliHIlg oxygen into an excess ALFRED FELIX sEBASnE N,sartorial 7 1

